slogloki

README

Forked and fixed to work in 2024.

slog: Loki handler

A Loki Handler for slog Go library.

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^{Sponsored by:}

Cloud-native search engine for observability - An OSS alternative to Splunk, Elasticsearch, Loki, and Tempo.

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See also:

• slog-multi: slog.Handler chaining, fanout, routing, failover, load balancing...
• slog-formatter: slog attribute formatting
• slog-sampling: slog sampling policy

HTTP middlewares:

• slog-gin: Gin middleware for slog logger
• slog-echo: Echo middleware for slog logger
• slog-fiber: Fiber middleware for slog logger
• slog-chi: Chi middleware for slog logger
• slog-http: net/http middleware for slog logger

Loggers:

• slog-zap: A slog handler for Zap
• slog-zerolog: A slog handler for Zerolog
• slog-logrus: A slog handler for Logrus

Log sinks:

• slog-datadog: A slog handler for Datadog
• slog-betterstack: A slog handler for Betterstack
• slog-rollbar: A slog handler for Rollbar
• slog-loki: A slog handler for Loki
• slog-sentry: A slog handler for Sentry
• slog-syslog: A slog handler for Syslog
• slog-logstash: A slog handler for Logstash
• slog-fluentd: A slog handler for Fluentd
• slog-graylog: A slog handler for Graylog
• slog-quickwit: A slog handler for Quickwit
• slog-slack: A slog handler for Slack
• slog-telegram: A slog handler for Telegram
• slog-mattermost: A slog handler for Mattermost
• slog-microsoft-teams: A slog handler for Microsoft Teams
• slog-webhook: A slog handler for Webhook
• slog-kafka: A slog handler for Kafka
• slog-nats: A slog handler for NATS
• slog-parquet: A slog handler for Parquet + Object Storage
• slog-channel: A slog handler for Go channels

🚀 Install

go get github.com/samber/slog-loki/v3

Compatibility: go >= 1.21

No breaking changes will be made to exported APIs before v4.0.0.

💡 Usage

GoDoc: https://pkg.go.dev/github.com/samber/slog-loki/v3

Handler options

type Option struct {
	// log level (default: debug)
	Level slog.Leveler

	// loki
	Client *loki.Client

	// optional: customize webhook event builder
	Converter Converter
	// optional: fetch attributes from context
	AttrFromContext []func(ctx context.Context) []slog.Attr

	// optional: see slog.HandlerOptions
	AddSource   bool
	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
}

Attributes will be injected in log payload.

Other global parameters:

slogloki.SourceKey = "source"
slogloki.ErrorKeys = []string{"error", "err"}
slogloki.SubAttributeSeparator = "__"
slogloki.AttributeKeyInvalidCharReplacement = "_"

Example

import (
	"github.com/grafana/loki-client-go/loki"
	slogloki "github.com/samber/slog-loki/v3"
	"log/slog"
)

func main() {
	// setup loki client
	config, _ := loki.NewDefaultConfig("http://localhost:3100/loki/api/v1/push")
	config.TenantID = "xyz"
	client, _ := loki.New(config)

	logger := slog.New(slogloki.Option{Level: slog.LevelDebug, Client: client}.NewLokiHandler())
	logger = logger.
		With("environment", "dev").
		With("release", "v1.0.0")

	// log error
	logger.Error("caramba!")

	// log user signup
	logger.Info("user registration")

	// stop loki client and purge buffers
	client.Stop()
}

Tracing

Import the samber/slog-otel library.

import (
	slogloki "github.com/samber/slog-loki"
	slogotel "github.com/samber/slog-otel"
	"go.opentelemetry.io/otel/sdk/trace"
)

func main() {
	tp := trace.NewTracerProvider(
		trace.WithSampler(trace.AlwaysSample()),
	)
	tracer := tp.Tracer("hello/world")

	ctx, span := tracer.Start(context.Background(), "foo")
	defer span.End()

	span.AddEvent("bar")

	logger := slog.New(
		slogloki.Option{
			// ...
			AttrFromContext: []func(ctx context.Context) []slog.Attr{
				slogotel.ExtractOtelAttrFromContext([]string{"tracing"}, "trace_id", "span_id"),
			},
		}.NewLokiHandler(),
	)

	logger.ErrorContext(ctx, "a message")
}

🤝 Contributing

• Ping me on twitter @samuelberthe (DMs, mentions, whatever :))
• Fork the project
• Fix open issues or request new features

Don't hesitate ;)

# Install some dev dependencies
make tools

# Run tests
make test
# or
make watch-test

👤 Contributors

💫 Show your support

Give a ⭐️ if this project helped you!

📝 License

Copyright © 2023 Samuel Berthe.

This project is MIT licensed.

Documentation

Index

• Variables
• func DefaultConverter(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, ...) model.LabelSet
• type Converter
  • func NewDataConverter(dataPrefix string, opts ...DataConverterOpt) Converter
• type DataConverterOpt
  • func DataConverterDataKeyOpt(key string) DataConverterOpt
  • func DataConverterErrorKeyOpt(keys ...string) DataConverterOpt
  • func DataConverterExemptDataPrefixOpt(prefix string) DataConverterOpt
  • func DataConverterSourceKeyOpt(key string) DataConverterOpt
  • func DataConverterUseImpliedOpt() DataConverterOpt
  • func DataConveterSetExemptKeys(keys ...string) DataConverterOpt
• type DataConverterOpts
  • func DefaultDataConverterOpts() *DataConverterOpts
• type LokiHandler
  • func (h *LokiHandler) Enabled(_ context.Context, level slog.Level) bool
  • func (h *LokiHandler) Handle(ctx context.Context, record slog.Record) error
  • func (h *LokiHandler) WithAttrs(attrs []slog.Attr) slog.Handler
  • func (h *LokiHandler) WithGroup(name string) slog.Handler
• type Option
  • func (o Option) NewLokiHandler() slog.Handler

Variables

var AttributeKeyInvalidCharReplacement = "_"

var ErrorKeys = []string{"error", "err"}

var SourceKey = "source"

var SubAttributeSeparator = "__"

See:

• https://github.com/samber/slog-loki/issues/10
• https://github.com/samber/slog-loki/issues/11

Functions

func DefaultConverter

func DefaultConverter(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) model.LabelSet

Types

type Converter

type Converter func(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) model.LabelSet

func NewDataConverter

func NewDataConverter(dataPrefix string, opts ...DataConverterOpt) Converter

type DataConverterOpt

type DataConverterOpt func(*DataConverterOpts)

func DataConverterDataKeyOpt

func DataConverterDataKeyOpt(key string) DataConverterOpt

func DataConverterErrorKeyOpt

func DataConverterErrorKeyOpt(keys ...string) DataConverterOpt

func DataConverterExemptDataPrefixOpt

func DataConverterExemptDataPrefixOpt(prefix string) DataConverterOpt

func DataConverterSourceKeyOpt

func DataConverterSourceKeyOpt(key string) DataConverterOpt

func DataConverterUseImpliedOpt

func DataConverterUseImpliedOpt() DataConverterOpt

func DataConveterSetExemptKeys

func DataConveterSetExemptKeys(keys ...string) DataConverterOpt

type DataConverterOpts

type DataConverterOpts struct {
	ErrorKeys        []string
	SourceKey        string
	DataKey          string
	ExemptDataPrefix string
	ExemptKeys       []string
	UseImplied       bool
}

func DefaultDataConverterOpts

func DefaultDataConverterOpts() *DataConverterOpts

type LokiHandler

type LokiHandler struct {
	// contains filtered or unexported fields
}

func (*LokiHandler) Enabled

func (h *LokiHandler) Enabled(_ context.Context, level slog.Level) bool

func (*LokiHandler) Handle

func (h *LokiHandler) Handle(ctx context.Context, record slog.Record) error

func (*LokiHandler) WithAttrs

func (h *LokiHandler) WithAttrs(attrs []slog.Attr) slog.Handler

func (*LokiHandler) WithGroup

func (h *LokiHandler) WithGroup(name string) slog.Handler

type Option

type Option struct {
	// log level (default: debug)
	Level slog.Leveler

	// loki
	Client *loki.Client

	// optional: customize webhook event builder
	Converter Converter
	// optional: fetch attributes from context
	AttrFromContext []func(ctx context.Context) []slog.Attr

	// optional: see slog.HandlerOptions
	AddSource   bool
	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
}

func (Option) NewLokiHandler

func (o Option) NewLokiHandler() slog.Handler

Creating a Loki client at each `NewLokiHandler` call may lead to connection leak when chaining many operations: `logger.With(...).With(...).With(...).With(...)`